The internal and external cooling fins in these Derale Cooling Products Heat Sink transmission coolers provide maximum cooling efficiency without relying on direct airflow. Their compact diameter means they can be mounted in a variety of locations, such as on the frame rail next to the transmission, directly under the radiator, under the floorboards, etc. The rugged aluminum extrusion features welded ends for long service life in even the toughest environments. These coolers are offered in several lengths with 3/8 in. inlets.